The Quasar from The Beginning of Time | STELLAR

A single, extremely distant quasar—found as a faint speck in the constellation Boötes—has become a time machine for probing the universe’s earliest era, when the cosmos was still cooling and the first stars were just beginning to change everything. In spring 2017, astronomers pointed the Gemini telescope at that target and used its infrared capabilities to dissect the quasar’s light. The quasar’s spectrum revealed a dramatic redshift: its light has been traveling for about 13.1 billion years, placing the object when the universe was only ~5% of its current age. That matters because it lets researchers study the transition period before reionization finished—an epoch when hydrogen gas made the early universe opaque, especially to ultraviolet light.

The observation hinges on why the quasar looks so “red.” As light crosses an expanding universe, its wavelengths stretch, shifting ultraviolet emission into infrared by the time it reaches Earth. Gemini’s Gemini North Infrared Spectrograph (GNIRS) breaks the incoming light into component wavelengths, producing a spectrum that carries both distance information and clues about the intervening gas. In this quasar’s spectrum, a broad blank region—an extended stretch of near-zero signal—signals how much early hydrogen absorbed ultraviolet photons. After the Big Bang, hydrogen filled space and blocked ultraviolet light; as the first stars and galaxies formed, their radiation eventually ionized that hydrogen in a process called reionization. This quasar shines from before that “job” was fully completed, offering a direct window into the murky-to-clear transformation.

The same spectral fingerprints used to measure redshift also broaden due to the extreme speeds of gas whipping around the quasar’s central supermassive black hole. Those broadened lines allow an estimate of the black hole’s mass at roughly 800 million Suns. The scale is staggering: such a black hole would have been able to swallow objects on the scale of Saturn’s orbit if it replaced our Sun. Yet it existed when the universe was still young, raising a long-standing puzzle—how could a black hole grow to that size in such a short cosmic time?

Gemini’s ability to make this measurement depends on more than just size. At Mauna Kea’s 4,200-meter summit, the observatory operates in cold, stable conditions to protect sensitive infrared instruments. Adaptive optics corrects atmospheric blurring in real time using a deformable mirror, while lasers create an artificial guide star by exciting sodium atoms high in the atmosphere. Together, these systems sharpen the quasar’s faint light enough for GNIRS to extract the spectrum.

Beyond the immediate mystery of black hole growth, the quasar observation opens new questions about early-universe physics and the timing of reionization. It also reinforces a broader trend in astronomy: while traditional telescopes map the universe through electromagnetic radiation, newer approaches—such as gravitational-wave detection at LIGO—can reveal phenomena through ripples in spacetime itself. For now, this single infrared spectrum from Gemini is both a revelation and a challenge, illuminating the universe’s earliest epochs while demanding better answers about how massive black holes formed so quickly.